I have a 1999 15 hp Suzuki four stroke outboard. Never really had much problems with it except carb stuff from letting it sit for a while. Anyway I took it out today on the Hillsborough river, I was going idle speed for about 15 minutes though the no wake zone. Then the zone ended so I took her up to full speed (as I normally do), she was running good for about 2 minutes and then I noticed the rpm's dropped slightly, so I took it right back to idle speed. As soon as it hit idle speed I just hear hissing and steam (not smoke) starts coming out of exhaust or pee stream, maybe both I don't remember. Then I just pulled the key and she shut off, I was hooking up my trolling motor and thought I give it another try, so I started it up again (one pull) and then more steam just started coming out so I turned it off and trolled back to the ramp. I thought it was weird that the steam started only when I hit idle speed? I'm not sure what it could be, but I think its most likely something in the cooling system, maybe a hose? I was hoping one someone on here would know.